This invention relates to an RF oscillator, and to a method of generating RF energy.
The generation of frequency stable microwave power presents certain difficulties. This is particularly so at frequencies of above about 2.5 GHz, where the use, in a phase lock loop, of digital frequency dividers coupled directly to the microwave output is no longer practical. The practice heretofore has normally been to use a separate harmonic generator, in the form of a non-linear device such as a snap recovery diode. This is used to generate, from the output of a frequency-stable relatively low frequency reference oscillator, a harmonic having a frequency close to the desired one. The output of the non-linear device is fed to a mixer, where local oscillator bias is provided by the microwave source. The resulting IF (frequency difference between the harmonic and the output of the microwave source) is then used in a control loop to control the frequency of the microwave source. The use of such a separate harmonic generator is expensive.
It is an object of the invention to provide a frequency stable RF oscillator in which use is made of inexpensive components.